1. Field of the Invention
The present invention is directed generally to a system and method for providing corrosion protection for mechanical locking devices and, more particularly, to a system and method for providing improved resistance to galvanic corrosion associated with a locking device.
2. Background of the Invention
Galvanic corrosion, also called “dissimilar metal corrosion” and sometimes “electrolysis”, refers to corrosive damage induced when two dissimilar materials are coupled together in the presence of a corrosive electrolyte. The more nobel a metal, the more cathodic it is on the galvanic series, while less nobel metals are more anodic on the galvanic series. A galvanic couple forms when one of the metals in the couple becomes an anode, causing it to corrode faster than it otherwise would, while the other metal in the couple becomes a cathode, and thus corrodes slower than it otherwise would. Additionally, it is not uncommon in practice for a cathodic metal to provide greater surface area than the anodic metal, thereby further exacerbating the reduction reaction, and increasing the corrosion of the anodic metal. It may also be noted that although the extent of corrosion may be greatest at the interface of the two dissimilar metals, corrosion may also occur at some distance away from the actual interface.
Historically, mechanical locking devices often fail, or need to be serviced, due to galvanic corrosion. Locking devices are often made of steel, and are often used with dissimilar metals, such as aluminum. For example, a tang, or locking ring, may be used. Steel is relatively nobel, or cathodic, while aluminum is a relatively active, or anodic. The interface of these two dissimilar metals may tend to create galvanic corrosion, causing in this example the aluminum to erode away. This may undesirably lead to an otherwise premature failure of the mechanical locking device, or steel tong.
Of course, the present invention is suitable for use with a wide variety of locking devices that secure something together, including by way of non-limiting example only, tongs, screws, bolts, nails and rivets, to name just a few.
Common methods of preventing galvanic corrosion have included covering the surfaces of the corroding metal with various types of paint; selecting combinations of metals that are from groups that are close together in the galvanic series; or plating with compounds such as cadmium and zinc. However, protective coatings such as paint historically fail to provide adequate protection against galvanic corrosion. Common limitations with these protective coatings include: degradation by exposure to the environment, and specifically to environmental elements such as ultra-violet light, acid rain, and saline environments; incomplete coverage of the metal surface by the protective coating; or the development of breaks in the protective coating through mechanical abrasion. More specifically, such protective coatings often do not adhere well to the metal substrate, allowing the coating to flake off or erode away. Additionally, some mechanical locking mechanisms, such as staking, defeat certain corrosion protection coatings by stripping away the protective layer upon installation allowing the two dissimilar base metals to come in contact with one another. Other conventional methods may suffer drawbacks as well.